Negative or Positive
Depending upon whether your company had originated from Western Union or from a later radio "upstart" like Marconi, your batteries might have either their negative or their positive terminals connected to ground. It's all part of the Great Debate about whether electrical Mother Earth has a negative or a positive tendency, and the effort to reduce cathodic erosion of grounding terminals in the plant. And that reflected into whether, on polar telegraph circuits, marking current was postive or negative. At ITT in NY, when we got circuits in from Western Union or WUI, their
marking current was always positive, and we'd have to match them, because they would not change!
When we got circuits in from RCA, they'd always be negative mark, and we'd have to match them, because they would not change! At ITT, we liked negative mark, but we'd adapt to the others, just to get business done. I can't imagine what must have gone on when the two of them tried to interconnect!
At any rate, you could see the historical heritage of Western Union and RCA in each of these. And what was our heritage that made ITT so accommodating?
Remember Postal Telegraph? That manually-run, scrambling around outfit owned by ITT that gave Western Union such fits pre-WWII that Western went to the FCC to sue ITT out of the domestic telegraph business? See, the story all fits together!